Genes involved in the early stages of sporulation should respond to changes in the external environment and then transduce this information as they become effectors for subsequent steps in the sporulation sequence. We have cloned the spoOH gene, one of the eight genes involved in the transition from vegetative growth to sporulation. Recent work from our laboratory has shown that the expression of the spoOH gene is regulated so that its gene product appears at the end of vegetative growth. The presence of high levels of glucose, which depresses sporulation, prevents the late growth activation of spoOH expression. We plan to examine factors involved in the initiation of sporulation, using spoOH gene expression as a tool for this analysis. We will obtain cis and trans mutations which alter spoOH expression and will study the transcription and translation of the spoOh gene, in vitro. To study the role of the spoOH protein in sporulation, we plan to ascertain, genetically and physically, whether this protein must interact with other cellular components as part of its obligatory role in the temporal sequence of development. Its role in sporulation will also be studied using in vitro transcription and translation systems.